Refrigerating system



1952 J. A. RATCLIFF 2,581,044

REFRIGERATING SYSTEM 2 Sl-lEETS-SHEET 1 Filed Sept. 17, 1949 ||||||I|| lllllllullllllllll INVENTOR. Jack 4. rPdfc/f %f Jan. 1, 1952 J. A.RATCLIFF REFRIGERATING SYSTEM 2 SHEETSSHEET 2 Filed Sept. 17, 1949 f 0 26. W iu LII! T m n n 7 L n Z ww "WM." QM v -L E n r am e n I Q Q 7 e u 6n a n n a m m n e o 0 a +12 0 u 5 z u F5 4 INVENTOR. Jack 6. Fafc/f/f 3%f '47 NEK Patented Jan. 1, 1952 UNITED STATES PATENT OFFICER-EFRIGERATING SYSTEM Jack A. Ratclifl, Amarillo, Tex.

Application September 17, 1949, Serial No. 116,300

14 Claims. (Cl. 62-2) The present invention relates in general torefrigerating apparatus and it deals more particularly with dualtemperature zone refrigerating apparatus of the primary-secondary type.

It is an object of the invention to provide refrigerating apparatus ofthe character indicated wherein the temperature of the zone refrigeratedby the primary system is adjustable and the zone refrigerated by thesecondary system automatically is maintained at substantially uniformtemperature despite adjustments made affecting the first mentioned zone.

Another object is to provide refrigerating apparatus of this typewherein the zone refrigerated by the secondary refrigeration system ismaintained at substantially uniform temperature regardless of theintermittent operation of the primary system.

A further object of my invention is to provide refrigerating apparatusof the primary-secondary type having an improved arrangement for theexchange of heat between the primary and secondary systems. Morespecifically it is an object to provide an arrangement for varying therate of heat exchange between the primary and secondary systems andautomatically controlling the variation in accordance with the needs ofthe secondary system.

One of the features of the invention lies in the provision of a primaryevaporator and a secondary condenser in heat exchange relation, the heatexchange being effected by a liquid whose level may be raised or loweredto alter the rate thereof.

Another feature resides in the provision of a novel arrangement forcontrolling the level of the aforementioned liquid in accordance withthe temperature of the secondary evaporator or the zone refrigerated byit.

Other and further objects together with the features of novelty by whichthe objects are achieved will appear in the course of the followingdescription of the invention.

In the accompanying drawings which form a part of the specification andare to be read in conjunction therewith, and in which like referencenumerals are employed to indicate like parts of the various views:

Fig. 1 is a schematic drawing of a refrigerator employing my improvedrefrigeration system,

Fig. 2 is an enlarged horizontal cross-section of the secondarycondenser of my refrigeration system, taken along lines 2-4 of Fig. 1 inthe direction of the arrows. the control bellows being shown incontracted condition,

Fi 3 is a vertical cross-section of the secondary condenser taken alongthe line 3-3 of Fig. 2 in the direction of the arrows,

Fig. 4 is a fragmentary cross-section of the lower part of the secondarycondenser, taken along line 44 of Fig. 2, the control bellows beingshown in expanded condition,

Fig. 5 is a side elevation of a modified form of secondary condenseraccording to the invention, part being broken away in order to show theposition of the control diaphragm whenthe solenoid is energized,

Fig. 6 is a horizontal cross-section taken along the lines 66 of Fig. 5in the direction of the arrows,

Fig. 7 is a vertical cross-section taken along line l-l of Fig. 6showing the position of the control diaphragm when the solenoid isde-energized, and

Fig. 8 is a schematic diagram of the circuits for controlling thesolenoid shown in Figs. 5 to 7 inclusive.

Referring more particularly to Fig. 1, the cabinet of a household orkitchen type refrigerator is indicated diagramatioally in dotted lines:This has a pair of hinged front doors I0 and H which, when opened, giveaccess respectively to an upper compartment l2 and a lower compartment[4, the two compartments being separated from one another by ahorizontal partition or baflle IS.

The lower compartment is designed for conventional refrigerated foodstorage, the optimum temperature of which is in the neighborhood of 40F. The upper compartment, on the other hand, is designed for freezingice cubes and freezing or holding in frozen condition the variouscomestibles placed therein; while its temperature may be varied oradjusted, as will be explained hereinafter, it preferably should bewithin the range of minus 10 F. to plus 15 F. For convenience indistinguishing between the two compartments, the upper one will bereferred to hereinafter as the freezer zone and the lower one as thestorage zone.

Each of these zones has its own cooling coil or evaporator, the one forthe freezer compartment being designated by the numeral [8 and the onefor the storage compartment by the numeral 20. It will be understoodthat the showing of both evaporators in Fig. 1 is largeli schematic, itbeing intended that in the case of either one the evaporator may be acompact unit within the compartment but occupying less than all thespace therein, or, alternatively, that the cooling coil may be formedwithin, or as a liner for, some or all of the walls of the compartmentin question.

The evaporator I8 and the evaporator 20 actually comprise parts of twoseparate closed refrigeration systems, the former evaporator being inthe primary system and the latter in the secondary system. The primarysystem also includes a compressor 22 and a primary condenser 24 whichare of any conventional or suitable construction and may be situated inthe bottom of the cabinet as shown, or in any other convenient location.The cooling coil 18 has one end connected to a downwardly extending duct28 which leads to the suction side of the compressor. Disposed alongsidethe major portion of this duct in heat exchange relation thereto is acapillary tube 28, the lower end of which is connected through astrainer 30 to the outlet of the condenser; the upper end of thecapillary tube is connected to the other end of coil I! through a heatexchange coil 32 which is looped back and forth in zig-zag fashionaround and in thermal contact with the shell 34 of a secondarycondenser.

As best seen in Figs. 2 and 3, the secondary condenser comprises adouble wall vessel having an outer shell 34 and a closely spaced innershell 36, the annular space between the two shells being somewhatexaggerated in the drawings, however, for the sake of clarity. Althoughthe vessels are illustrated as concentric cylinders having parallelvertical walls, they may be of other shapes, having, for example,upwardly or downwardly converging walls, the effect of which will beevident from the ensuing description. Both ends of the storage zoneevaporator 20 communicate with the inner vessel, one end being connectedthereto by a-tube 33 which terminates flush with the bottom of thevessel and the other by a tube which extends up to a point near the topof the vessel; both tubes are soldered or otherwise sealed relative thevessel where they enter same. The inner vessel contains a suitablerefrigerant such as Freon and, together with evaporator 20, comprisesthe closed secondary refrigeration system.

It will be convenient at this point to briefly outline the refrigerationcycle of the primary and secondary systems, and the thermal relationbetween the two. Referring first to the primary system, the compressor22 draws the heat laden vaporized refrigerant from the evaporator itthrough the suction line 26, compresses the vapor and discharges itunder high pressure into the primary condenser 24. In the primarycondenser the vapor condenses and in changing into liquid phase gives upits heat to the ambient air. The liquid refrigerant then passes throughthe strainer 30 into the capillary tube 28 where it is conducted to thesecondary heat exchange coil 32. The latter coil is of greatercrosssectional area than the capillary tube, so that the pressure, andhence the temperature, of the refrigerant liquid is reduced on enteringcoil 32.

Since coil 32 is tightly clamped around the secondary condenser, it willrefrigerate the latter. A mixture of low pressure liquid and vaporpasses out of the secondary heat exchanger coil 32 to the top of theevaporator 18. In the evaporator it takes up heat from the uppercompartment l2, refrigerating the latter, and the vaporized refrigerantthen is drawn back to the compressor through the suction line 26; thecomparatively cool suction vapor passing through this line absorbs someof the heat from the liquid passing through the capillary tube 23 whichis in heat exchange relation thereto, and this considerably increasesthe efficiency of the primary system.

The refrigeration effect of the secondary heat exchange coil 32condenses the vaporized refrigerant in the upper portion of vessel 35.This reduces the pressure in the vessel and accordingly the liquidrefrigerant in the secondary evaporator 20 starts vaporizing. Thecondensed refrigerant in the vessel 36 drains out through tube 38 andenters the bottom of evaporator 20 in liquid phase; the vapor formed inthe evaporator at the same time leaves the top thereof and passesupwardly through tube 40 back into the vessel 33 completing the cycle ofthe secondary system.

The electrical connections controlling the compressor have been omittedfrom the drawings for the sake of clarity since they are conventionaland form no part of the present invention; as is well understood bythose versed in the art, the

compressor preferably is so operated as to maintain the zonerefrigerated by evaporator l3 at a relatively constant temperature,which temperature is selectable or adjustable within predeterminedlimits. Customarily this is accomplished by operating the compressorunder control of a manually adjustable thermostat located in therefrigerated zone (clamped on the evapora tor It, for example) but aspreviously suggested, any suitable arrangement for selecting thetemperature and automatically maintaining the selected temperature inthe freezer zone l2 may be employed.

Whatever the nature of the temperature control for the primaryrefrigeration system, it will be evident that when the refrigerationeffect upon the freezer compartment i2 is increased or decreasedincident to altering the selected temperature of the compartment, thereis a corresponding increase or decrease in the refrigeration effect ofcoil 32 upon the secondary condenser. Consequently, there is a tendencyfor a change in the control of the primary refrigeration system to bereflected by a corresponding change in the secondary system, with theresult that the temperature of storage compartment i4 tends to shift upor down. Such a shift, however, would be very undesirable for if thetemperature in the storage compartment shifts upwardly from the narrowoptimum range, the perishable foodstuifs therein are not suihcientlyrefrigerated to prevent bacterial action; on the other hand, if thetemperature shifts downwardly from the optimum value it results in unduedehydration of the foodstuffs.

It is an important feature of the present invention that the temperatureof the storage compartment l4 remains substantially constant regardlessof adjustments made to raise or lower the temperature of the freezercompartment l2 and regardless of other factors that might otherwise tendto disturb the temperature of the storage compartment. The manner inwhich this result is achieved now will be described.

Referring to Figs. 1, 2 and 4 it will be seen that the shell 34 of thesecondary condenser is provided with a laterally extending integralhousing 42 containing a bellows 44, to which bellows a bulb 46 isconnected by a small tube 48 entering the housing through a suitableseal or packing gland. Preferably the bulb is located in the storagezone M as shown, or, to achieve the same end, clamped on the evaporator20 near the outlet thereof; if desired, however, it may be situated incompartment l2 or otherwise associated with evaporator l8.

The bellows, tube and bulb comprise a hermetically sealed unitcontaining a thermo-expansive gas such as Freon. Thus, as the bulb 46 iswarmed the gas expands, expanding the bellows (see Fig. 4) and when itis cooled, the gas contracts, contracting the bellows (see Fig. 2).Around the bellows and in the space between the walls of vessels 34 and36 is a heat conducting inner vessel as shown in Fig. 3; but when thebellows fully expands, the liquid is forced upwardly in the annularspace between the inner and outer walls, raising the level to a point ator near the top of the vessel.

The function of liquid 50 is to vary the rate of heat transfer betweenthe inner and outer shells of the secondary condenser. Because thethermo conductivity of the liquid is high as compared to the thermoconductivity of air, the refrigeration effect produced by coil 32 uponthe secondary system is greatest when the space between the inner andouter shells of the secondary condenser is filled with liquid, and isleast when the liquid level drops so that the space is filled only withair. Between these maximum and minimum conditions of heat transfer thereare, of course, innumerable intermediate values, each depending upon theexact position of the surface of the liquid between the aforementionedupper and lower limits of its travel.

For purposes of illustrating the operation of my device let it beassumed that compartment I2 is at F., compartment 14 at 40 F., and thatunder these conditions the surface of liquid 50 is at a levelapproximately midway between the top and bottom of vessel 36. In theevent door II is opened for an appreciable interval, some of the coolair in compartment I4 is replaced by warm air, and the consequentwarming of bulb 46 causes bellows 44 to expand as explainedhereinbefore. This raises the level of liquid 50 so that heat isextracted from the secondary refrigeration system by coil 32 morerapidly than before; as the temperature in compartment 14 now drops dueto the increased refrigeration effect of the secondary system, the levelof liquid 50 also drops, slowing down the rate of heat transfer andpreventing the food storage compartment I4 from becoming too cool.

Suppose now that the activity of the primary refrigeration system isincreased, either as the result of frequent or prolonged opening of doorID, or as a result of a re-setting of a thermostatic control to makecompartment l2 colder than before. This naturally increases therefrigeration effect of coil 32 upon the secondary system and begins toreduce the temperature ofcompartment M; however, when this occurs,bellows 44 begins to contract under control of bulb 46, lowering thelevel of liquid 50 and reducing the rate at which heat is extracted fromthe secondary system. Thus it will be seen that whether therefrigeration effect of the primary system is accelerated ordecelerated, such compensation will automatically be effected by liquid50 as will maintain the refrigeration of compartment l4 substantiallyuniform.

A modified arrangement for achieving the same end by electrical controlrather than purely mechanical control is shown in Figs. to B inclusive.Here there has been substituted for the bellows of the secondarycondenser a two-piece housing 50 having a flexible diaphragm 52 clampedbetween the two halves. This housing is .supported on the secondarycondenser by a pipe 54 through which the chamber below the diaphragmcommunicates with the interior of shell 34. Above the housing is asolenoid 5-6 whose vertically shiftable core 58 is connected to thediaphragm as shown; Fig. 5 illustrates the position of the diaphragmwhen the solenoid is energized, and Figs. 7 and 8 show its position whenthe solenoid is de-energized. It will be understood that under theformercondition the surface of liquid 50 is at or near the bottom of the innervessel 36 and that under the latter condition it is at or near the topof the vessel. Except for this modification in the arrangement forcontrolling the liquid level, the structure and relationship of theprimary and secondary refrigeration systems is as previously described.

Fig. 8 is a schematic diagram of the circuit for controlling thesolenoid and the compressor motor. Numeral 60 indicates a switchthermostatically controlled by the compartment or evaporator temperaturein the freezer zone l2, and numeral 62 indicates a switchthermostatically controlled by the compartment or evaporator temperaturein the food storage zone H. Each switch will shift to its high positionwhen the temperature of the associated thermostat rises to or above theupper limit for which it has been set, and will shift to its low"position when the thermostat temperature drops to or below the lowerlimit for which it has been set. As is conventional, it should beunderstood that each thermostat is adjustable in order to vary the upperand lower limits of its operation.'

Considering the circuit operation more in detail, it will be seen thatwhen either switch is in its high position (which means that theassociated compartment or evaporator has reached as high a temperatureas is desirable and hence that it is a need of refrigeration) a circuitis completed through that switch from conductor 64 of the power line toconductor 66.

of the compressor motor; the other side of the motor (68) is connecteddirectly to the remaining power conductor 10, so the compressor willoperate, supplying the necessary refrigeration as long as eithercompartment needs it, that is, as long as the associated switch 60 or 62remains in its high position.

It also will be noted that so long as switch 62 is in its high"position, solenoid 56 remains de-energized and hence, as shown in Fig.7, the heat transfer liquid 50 completely fills the space between theinner and outer shells 34 and 36 of the secondary condenser.Accordingly, it will be clear from the earlier explanation that the heatis extracted from the secondary refrigeration system at the maximum ratein order that the evaporator in the food storage zone ll will supply itsmaximum refrigerating effect.

In the event that switch 62 shifts to its "low" position while switch 60remains in the "high" position, solenoid 56 is energized over a circuitwhich extends fromsupply conductor 64 through switch 60 thence throughthe solenoid winding, switch 62 and back to the power supply conductor10. The energization of the solenoid causes liquid 50 to drop as shownin Fig. 5, im-- mediately reducing the rate of heat transfer between theinner and outer shells of the secondary condenser; by reducing therefrigeration effect of the secondary system, this prevents thetemperature in the food storage zone l4 from dropping too low eventhough the primary system is continuing to refrigerate the freezer TonI2 at its maximum rate.

When switch 60 shifts to its low position, t e aforementioned circuitfor the comprezsor motor is opened halting the same; at the state timethe circuit for solenoid 56 also is opened, as a result of which liquid50 is again raised to its uppermost level insuring that the secondaryrefrigeration system gets maximum benefit of the now reducedrefrigeration eflect of coil 32.

The system now will remain in this condition until one or the other ofthe compartments becomes warm enough to shift the associated switch toits "high position. If it is switch 62 which operates first this willstart the compressor without re-energizing thesolenoid and thus insurethat the associated food storage zone 14 receives the maximum benefit ofthe refrigeration cycle. If, on the other hand, it is switch 80 whichoperates first, this will not only start the compressor but willre-energize the solenoid insuring that the freezer zone I: is suppliedthe necessary refrigeration without over-cooling the storage zone 14.

It will be clear from the foregoing description and explanation that thesalient novelty of my invention resides in the construction andrelationship of the primary and secondary refrigeration systems andparticularly in the arrangement whereby I vary the heat transfer betweenthe two systems. The character of the cabinet or cabinets housing theevaporator or cooling coils of the respective systems is of onlyincidental importance and is subject to many variations withoutdeparting from the invention. The freezer and storage zones may, forexample, be separate compartments in the same cabinet as shown, or maybelocated in two separate and independent cabinets; alternatively, theymay not onhr be in the same cabinet but may be in limited communicationwith one another, for example, by the provision of apertures or ports inthe baflie I, or by the provision of a single unitary door opening bothcompartments simultaneously rather than selectively by separate doors.

It should also be understood that I do not wish to be limited to the useof any particular refrigerant in either the primary or the secondaryrefrigerating system, or, to any particular liquid for my heat transferliquid 50, it only being necessary that the liquid have adequate thermoconductivity and that it remain in liquid phase at all temperatures towhich it is subjected in the normal operation of the apparatus. Variousgases likewise may be employed for expanding and contracting the bellowsM under control of bulb l6 and my invention contemplates the use of anysatisfactory gas or mixture of gases for this purpose.

Inasmuch as many possible embodiments of the invention may be madewithout departure from the scope thereof, it is to be understood thatall matter herein set forth or shown in the accompanying drawings is tobe interpreted as illustrative and not in a limiting sense.

From the foregoing it will be apparent that this invention is one welladapted to attain all of the ends and objects hereinbefore set forthtogether with other advantages which are obvious and which are inherentto the apparatus.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by Ed is within the scope of theappended claims.

Having thus described my invention, I claim:

1. In refrigerating apparatus, a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a heat exchanger constructed and arranged toconduct heat from the secondary condenser to said first portion of theprimary evaporator. a low temperature compartment cooled by the secondportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, and said heat exchanger including means controlledconjointly by both of said devices for varying the rate of heat transferfrom the secondary condenser to said first portion of the primaryevaporator.

2. In refrigerating apparatus. a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a heat exchanger constructed and arranged toconduct heat from the secondary condenser to said first portion of theprimary evaporator, a low temperature compartment cooled by the secondportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, said heat exchanger including means controlledconjointly by both of said devices for varying the rate of heat transferfrom the secondary condenser to said first portion of the primaryevaporator, said last means operative at times to increase said rate ofheat transfer responsive to an increase in the temperature of the highertemperature compartment and operative at other times to increase saidrate of heat transfer responsive to a reduction in the temperature ofthe lower temperature compartment.

3. In refrigerating apparatus, a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a heat exchanger constructed and arranged toconduct heat from the secondary condenser to said first portion of theprimary evaporator, a low temperature compartment cooled by the secondportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, said heat exchanger including means controlledconjointly by both of said devices for varying the rate of heat transferfrom the secondary condenser to said first portion of the primaryevaporator, said last means operative at times to reduce said rate ofheat transfer responsive to a reduction in the temperature of the hightemperature compartment and operative at other times to reduce said rateof heat transfer responsive to an increase in the temperature of thelower temperature compartment.

4. In refrigerating apparatus, a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a heat exchanger constructed and arranged toconduct heat from the secondary condenser to said first portion of theprimary evaporator, a low temperature compartment cooled by the secondportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, said heat exchanger including means controlledconjointly by both of said devices ior varying the rate of heat transferfrom the secondary condenser to said first portion of the primaryevaporator, said last means constructed and arranged to maintain saidrate of heat transfer at a minimum whenever the lower temperaturecompartment is above a predetermined temperature and the highertemperature compartment concurrently is below a predeterminedtemperature, and said last means controlled by said devices to increasethe rate of heat transfer responsive either to the lower temperaturecompartment dropping below said first predetermined temperature or thehigher temperature compartment rising above said second predeterminedtemperature.

5. In refrigerating apparatus, a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, a

secondary refrigerant circuit including a secondary evaporator and asecondary condenser, a heat exchanger constructed and arranged toconduct heat from the secondary condenser to said first portion of theprimary evaporator, a low temperature compartment cooled by the secondportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, a compressor for said primary refrigerant circuitcontrolled conjointly by both of said devices to operate whenever thetemperature in either compartment rises above a predetermined minimumvalue for that compartment, and said heat exchanger including meanscontrolled conjointly by both of said devices for varying the rate ofheat transfer from the secondary condenser to said first portion of theprimary evaporator.

6. In refrigerating apparatus, a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a heat exchanger constructed and arranged toconduct heat from the secondary condenser to said first portion of theprimary evaporator, a low temperature compartment cooled by the secondportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein :that compartment, a compressor for said primary refrigerant circuitcontrolled conjointly by both of said devices to operate whenever thetemperature in either compartment rises above a predetermined minimumvalue for that compartment, and said heat exchanger including meanscontrolled conjointly by both of said devices for varying the rate ofheat transfer from the secondary condenser to said first portion of theprimary evaporator, said last means operative at times to increase saidrate of heat transfer responsive to an increase in the temperature ofthe higher temperature compartment above said predetermined minimumvalue for that compartment and operative at other times to increase saidrate of heat transfer responsive to a reduction in the temperature ofthe lower temperature compartment below said predetermine 1 minimum forthat compartment.

7. In refrigerating apparatus, a primary re- 10 frigerant circuitincluding a primary evaporator having a first portion and a secondportion, a secondary refrigerant circuit including a secondaryevaporator and a secondary condenser. a heat exchanger constructed andarranged to conduct heat from the secondary condenser to said firstportion of the primary evaporator, a low temperature'compartment cooledby the second portion of the primary evaporator, a higher temperaturecompartment cooled by the secondary evaporator, each of saidcompartments having a thermo-responsive device controlled in accordancewith the temperature in that compartment, a compressor for said primaryrefrigerant circuit controlled conjointly by both of said devices tooperate whenever the temperature in either compartment rises above apredetermined minimum value for that compartment, said heat exchangerincluding means controlled conjointly by both of said devices forvarying the rate of heat transfer from the secondary condenser to saidfirst portion of the primary evaporator, said last means operative attimes to reduce said rate of heat transfer responsive to a reduction inthe temperature of the higher temperature compartment below saidpredetermined minimum value for that compartment and operative at othertimes to reduce said rate of heat transfer responsive to an increase inthe temperature of the lower temperature compartment above saidpredetermined minimum value for that compartment.

8. In refrigerating apparatus, a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a low temperature compartment cooled by said firstportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, a variable heat exchanger for conducting heat fromthe secondary condenser to the second portion of the primary evaporator,said exchanger comprising an intermediate chamber between the secondarycondenser and said second portion, a liquid storage reservoircommunicating with said intermediate chamber, and means controlledconjointly by both of the said thermoresponsive devices for at timestransferring liquid from said reservoir into said chamber and at othertimes transferring liquid from} ;said chamber into said reservoir.

9. In refrigerating apparatus, a primary refrigerant circuit including aprimary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a low temperature compartment cooled by the firstportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with a temperature inthat compartment, a variable heat exchanger for conducting heat from thesecondary condenser to the second portion of the primary evaporator,said exchanger comprising an intermediate chamber between the secondarycondenser and said second portion, a liquid storage reservoircommunicating with said intermediate chamber, and means controlledconjointly by said thermo-responsive devices for at times transferringliquid from said reservoir into said chamber responsive to an increasein the temperature of the higher temperature compartment and at othertimes transferring liquid from said reservoir into said chamberresponsive to a decrease in temperature of the lower temperaturecompartment.

10. In refrigerating apparatus, a primary refrigerant circuit includinga primary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a low temperature compartment cooled by the firstportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with a temperature inthat compartment, a variable heat exchanger for conducting heat from thesecondary condenser to the second portion of the primary evaporator,said exchanger comprising an intermediate chamber between the secondarycondenser and said second portion, a liquid storage reservoircommunicating with said intermediate chamber, and means controlledconjointly by said thermo-responsive devices for at times transferringliquid from said chamber into said reservoir responsive to a decrease ofa temperature of the higher temperature compartment and at other timestransferring liquid from said chamber into said reservoir responsive toan increase in the temperature of the lower temperature compartment.

11.-In refrigerating apparatus, a primary refrigerant circuit includinga primary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a low temperature compartment cooled by said firstportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, a variable heat exchanger for conductin heat fromthe secondary condenser to said second portion of the primaryevaporator, said exchanger comprising an intermediate chamber betweenthe secondary condenser and said second portion, a closed liquid storagereservoir communicating with said intermediate chamber, one wall of saidreservoir comprising a flexible membrane, a plunger engaging saidmembrane and movable to flex the membrane thereby to vary the liquidcapacity of said reservoir, and means controlled conjointly by boththermo-responsive devices for moving said plunger thereby to transferliquid from said reservoir into and out of said intermediate chamber.

12. In refrigerating apparatus, a primary refrigerant circuit includinga primary evaporator havin a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a low temperature compartment cooled by said firstportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, a variable heat exchanger for conducting heat fromthe secondary condenser to the second portion of the primary evaporator,said exchanger comprising an intermediate chamber 12 between thesecondary condenser and said second portion. a closed liquid storagereservoir communicating with said intermediate chamber, one wall of saidreservoir comprising a flexible membrane, a plunger engaging saidmembrane and movable to flex the membrane thereby to vary the liquidcapacity of said reservoir and thus transfer liquid from said reservoirinto and out .of said intermediate chamber, a solenoid for actuatingsaid plunger, and temperature controlled means for intermittentlyenergizin said solenoid.

13. In refrigerating apparatus, a primary refrigerant circuit includinga primary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a low temperature compartment cooled by said firstportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that compartment, a variable heat exchanger for conducting heat fromthe secondary condenser to said second portion of the primaryevaporator, said exchanger comprising an intermediate chamber betweenthe secondary condenser and saidsecond portion, a liquid storagereservoir communicating with said intermediate chamber, means forvarying the liquid capacity of said reservoir thereby to transfer liquidfrom said reservoir into and out of said intermediate chamber, asolenoid for actuating said means, and a circuit for said solenoidincludin a pair of switches controlled respectively by saidthermo-responsive devices.

14. In refrigerating apparatus, a primary refrigerant circuit includinga primary evaporator having a first portion and a second portion, asecondary refrigerant circuit including a secondary evaporator and asecondary condenser, a low temperature compartment cooled by said firstportion of the primary evaporator, a higher temperature compartmentcooled by the secondary evaporator, each of said compartments having athermo-responsive device controlled in accordance with the temperaturein that com partment, a variable heat exchanger for conducting heat fromthe secondary condenser to said second portion of the primaryevaporator, said exchanger comprising an intermediate chamber betweenthe secondary condenser and said second portion, a liquid storagereservoir communicating with said intermediate chamber, means forvarying the liquid capacity of said reservoir thereby to transfer liquidfrom said reservoir into and out of said intermediate chamber, asolenoid for actuating said means, a circuit for said solenoid includinga pair of switches controlled respectively by said thermoresponsivedevices, and a compressor for said primary refrigerant circuitcontrolled conjointly by said switches.

JACK A. RATCLIFF.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,887,687 Killeffer Nov. 15, 19321,951,496 Stevens Mar. 20, 1934 2,116,389 Fiene May 3, 1938 2,492,648McCloy Dec. 27, 1949

